This invention concerns a mechanism and a method for supplying weft threads on weaving machines.
As is generally known, on weaving machines the weft threads are supplied to the shed by first winding them off yarn packages or the like by means of thread supply mechanisms and then inserting them into the shed. These thread supply mechanisms include prewinders formed by drums on which a quantity of thread is wound, so that a number of turns can be drawn off at each weaving cycle, thereby providing the required length of weft thread per insertion. The thread supply mechanisms also include insertion mechanisms for inserting the drawn off lengths of weft thread one by one into the shed. When making a cloth which contains different kinds of weft thread, for example weft threads of different colors or weft threads of different types, it is known to use at least as many weft supply mechanisms as there are used different kinds of weft threads.
On modern weaving machines, the aim is to automate them as far as possible in order to avoid weaving machine stops or to reduce stops to a minimum. In order to limit weaving machine stops due to faults in the weft thread supply, it is known from Belgian patent No. 901.969 held by the present applicant to hold a reserve mechanism in readiness for each weft supply mechanism. When a fault in the supply of a weft thread occurs, the machine automatically switches over to the reserve mechanism with the same type of weft thread. Although machine stops can be avoided with this known mechanism, it has the disadvantage that the weft supply mechanisms must be duplicated, so that the weaving machine is bulkier and also considerably more expensive than a conventional weaving machine.